#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); i++)
template<typename T> inline bool chmax(T &a, T b) {return ((a < b) ? (a = b, true) : (false));}
template<typename T> inline bool chmin(T &a, T b) {return ((a > b) ? (a = b, true) : (false));}
typedef long long ll;
typedef pair<ll,ll> P;



int main() {
    ll A, B, a, b;
    cin >> A >> B >> a >> b;

    ll x = A + a;
    while(1) {
        if(x % B == b) {
            cout << x << endl;
            break;
        }
        x += A;
    }


    return 0;
}